A quantum dot is a material having a crystalline structure only a few nanometers in size, and is composed of about a few hundred atoms to about a few thousand atoms. Since the quantum dot is very small, a quantum confinement effect occurs therein. The quantum confinement effect refers to a phenomenon in which when an object is reduced to a nano size or less, an energy band gap of the object is increased. Accordingly, when light of a wavelength having energy higher than the energy band gap is incident onto the quantum dot, the quantum dot absorbs energy of the light so that an energy level of the quantum dot is excited into an excited state, and then the energy level of the quantum dot drops to a ground state while the quantum dot is emitting light having a specific wavelength. The wavelength of the emitted light is determined by energy corresponding to the band gap.
In general, the smaller the particle of a quantum dot is, the shorter the wavelength of light emitted is, and the larger the particle of the quantum dot is, the longer the wavelength of light emitted is. These are distinct electrical and optical properties different from those of existing semiconductor materials. Therefore, desired light emitting characteristics of the quantum dot may be implemented by controlling the size, composition and the like of the quantum dot.